The Gironde Estuary is located in Southwestern France and is the primary body of water the impacts the Bordeaux Region of France. It opens on the Atlantic Ocean where the entrance is marked by the historic lighthouse of Cordouan. The Gironde is more than 80 kilometers in length and is formed where the Garonne River and the Dordogne River converge near Bourg. The Garonne River extends 360 miles and is formed to the Northeast in the Central Mountains of France. The Dordogne is nearly as long as the Garonne. It runs east and then south all the way to the Pyrenees Mountains that divide France and Spain.